Twin filament lamp



Nov. 19, 1968 G. A. CURL 3,412,276

TWIN FILAMENT LAMP Filed Feb. 2, 1967,

FIG. 2

47 4e 43 RED BLUE FIG. 4

s4 52 49 5s 5s 57 SON-5| lNVE/VTOR GERALD A. CURL Y wowafiAMa ATTORNEYS United States Patent 3,412,276 TWIN FILAMENT LAMP Gerald A. Curl, Van Nuys, Calif., assignor to Coastal Dynamics Corporation, a corporation of California Filed Feb. 2, 1967, Ser. No. 613,577 Claims. (Cl. 313--114) ABSTRACT OF THE DISCLOSURE This disclosure relates to a miniature lamp in the form of a single elongated transparent enclosure such as a glass tube having first and second filaments respectively disposed in opposite ends of the enclosure. Suitable lead out wires are provided for each of the filaments and arranged to be connected in parallel in a circuit such that should one of the filaments become broken or fail, the other filament will remain energized. The miniature lamps are best suited for annunciator systems, edge-lighted panels, and like applications where redundancy is required for safety purposes. The filaments are preferably disposed in planes at right angles to each other within the tube so that when both are energized, fairly uniform illumination is provided omni-directionally from the lamp.

This invention relates to miniature lamps and more particularly to a novel twin filament lamp for use with annunciator systems, edge-lighted panels, and similar applications.

:In applications of the foregoing type, there are very strict requirements with respect to the degree of illumination and redundancy in the provision of light for safety purposes, particularly when used in aircraft. This latter requirement has, for example, necessitated providing twice as many lamps as would normally be necessary to provide proper illumination. By such an arrangement, should some of the lights fail, there will still be sutficient illumination to enable proper reading of the nomenclature on the panels to satisfy safety requirements.

To provide more than the actual number of lamps necessary to perform a desired function is not only expensive but insuflicient insofar as weight and bulk of a panel board or other structure incorporating the lamps are concerned. However, there has not been evidence heretofore of any way of avoiding this problem.

Accordingly, it is a primary object of the present invention to provide a novel lamp structure which will substantially eliminate the foregoing problems.

More particularly, it is an object to provide a novel lamp structure wherein illumination of proper intensity is provided and yet which does not occupy substantially more space than conventional lamps and yet which still provides a redundant feature to satisfy safety requirements, all to the end that more reliable, lighter weight, and less bulky panel and annunciator structures than heretofore available can be realized.

Briefly, this and many other objects and advantages of this invention are attained by providing a miniature lamp structure in the form of a single elongated enclosure incorporating twin filaments. More particularly, the device contemplates first and second filaments disposed at opposite ends of the tubular structure, each being provided with independent electrical connecting means so that they may be individually energized. In accord with a unique feature of this invention, the filaments are oriented in planes at right angles to each other so that fairly uniform illumination is provided when both filaments are energized. By connecting the filaments in parallel with the energizing circuit, failure of one filament will not affect the other filament so that a desired redundancy is provided the same as if two independent lamps had been provided. The unique structure of the single enclosed twin filament lamp, however, avoids the problem of providing twice as many individual lamps and also results in a far less bulky and a far lighter panel arrangement than has heretofore been available.

In accord with further features of the invention, the dual filament lamp structure of this invention is susceptible to modification by providing a central opaque partition and cooperating sleeve-like color filters receivable over the ends of the tubular structure. With this arrangement, one lamp may be employed to provide illumination of two different colors to two different objects.

In preferred designs of the twin filament lamp, the electrical connecting means to the filaments may be brought out to band and end contacts such that the structure resembles a fuse and thus may readily be connected into a cradling socket structure having spring terminals and end terminals for engaging the respective electrical band and end contacts on the lamp itself. This arrangement provides for easy removal and replacement of the lamps.

A better understanding of the invention will be had by now referring to preferred embodiments thereof as illustrated in the accompanying drawings, in which:

FIGURE 1 is a perspective view of a basic twin filament lamp constructed in accordance with the present invention;

FIGURE 2 is a cross section taken in the direction of the arrows 22 of FIGURE 1;

FIGURE 3 is an exploded perspective view of a modified twin filament lamp and cooperating cradling and supporting structure;

FIGURE 4 is a cross section of a further modified twin filament lamp structure in accordance with the invention; and

FIGURE 5 is a cross section of a still further modified structure in accordance with the invention.

Referring both to FIGURES 1 and 2, the lamp comprises an elongated enclosure 10 preferably of glass and tubular shaped as shown. Within the enclosure there are disposed first and second filaments 11 and 12 of general U-shape as shown. The legs of the U-shape for the first filament 11 connect respectively to a first mounting means in the form of elongated conducting members 13 and 14 which may include outer ceramic type insulation or other rigid structural material for supporting the filament 11 with the U portion thereof extending toward the center of the tubular enclosure 10 and lying in a first plane. Suitable electrical connecting means in the form of lead out flexible wires 15 and 16 electrically connect to the mounting means 13 and 14 and thus to the legs of the filament 11.

In a similar manner, the filament 12 is generally U-shaped with its legs secured to a second mounting means in the form of rigid members 17 and 1 8, the U portion of the second filament extending toward the center of the tubular enclosure and lying in a second plane. Suitable flexible lead out wires 19 and 20 connect to the second mounting means 17 and 18 respectively. As will be evident from both FIGURES 1 and 2, the first and second planes of the filaments are disposed at right angles to each other.

With particular reference to FIGURE 2, suitable sealing to the glass enclosure 10 may be provided for the mounting means such as indicated at 21 and 22. In this respect, it will be noted from the cross-hatching that the mounting structure itself is of conductive material so that energization of the filament can be effected through the lead out wires and the mounting for the filament.

In the embodiment of FIGURES 1 and 2, the lead out wires are preferably connected in parallel to an energizing circuit so that the respective filaments are energized in dividually. As a consequence of orienting the respective filaments in planes at right angles to each other, it will be evident that the illumination from the elongated tubular enclosure will be substantially uniform omni-directionally about the tube.

In FIGURE 3, there is shown a modified structure wherein there is provided again an elongated glass enclosure 23 of tubular shape incorporating first and second filaments '24 and 25 mounted in planes at right angles to each other. A first mounting means 26 and 27 supports the filament 24 and connects to a first band contact 28 and a first end contact 29. Similarly, the second filament 25 is supported by a second mounting means 30 and 31 connecting to a second band contact 32 and a second end Contact 33.

It will be evident from the embodiment of FIGURE 3 that the electrical connecting means to the mounting means takes the form of band and end contacts, the two band contacts being disposed about the ends of the tubular enclosure 23 and the two end contacts being disposed centrally at the extreme opposite ends of the tubular structure.

The foregoing arrangement renders the twin filament lamp suitable for easy removal and replacement from a cooperating supporting cradle structure. This structure comprises a base member 34 mounting a flat conducting plate 35 to which suitable spring terminals .36 and 37 are afiixed. The conducting plate 35 electrically connects the spring terminals 36 and 37 together. On the opposite side of the base member 34, there is provided a second conducting plate 38 terminating in upturned ends 39 and 40 defining end terminals. Suitable leads may be connected to the plates 35 and 38 as indicated at 41 and 42.

With the foregoing arrangement, it will be evident that when the elongated enclosure 23 is inserted into the cradle support, the band contacts 28 and 32 will be engaged by the spring terminals 36 and 37 such that the band contacts will both be connected to the plate 35 and thus the lead 41. The end contacts 29 and 33, on the other hand, will be engaged by the end terminals 39 and 40 and will thus be connected together by the lower plate conductor 38 and to the lead 42. The respective filaments 24 and 25 will accordingly be connected in parallel and the failure of either one of the filaments will not affect operation of the other.

Referring now to FIGURE 4, there is shown a further modification of the structure wherein again there is provided an elongated enclosure 43 incorporating first and second filaments 44 and 45 supported by suitable mounting means in a manner similar to the structure illustrated in FIGURE 1, except that the planes of the filaments are not at right angles to each other. In the embodiment of FIGURE 4, there is provided an opaque partition 46 within the tubular enclosure 43 separating the filaments 44 and 45. Also provided are color filter structures 47 and 48 receivable over opposite ends of the enclosure 43 such that light from the-filament 44 will pass through the filter 47 and light from the filament 45 will pass through the filter 48. By this arrangement, a single lamp structure may be employed to illuminate nomenclature with ditterent colors.

FIGURE 5 shows yet a further modification of the invention similar in certain respects to the embodiment of FIGURE 3. In FIGURE 5, there is provided an elongated tubular glass enclosure 49 within which there are disposed first and second filaments 50 and 51, the filament 59 connects through mounting means 52 and 53 to band and end contacts 54 and 55. The filament 51 connects through mounting means 56 and 57 to band contact 58 and end contact 59. Thus far, the structure is the same as described in conjunction with FIGURE 3. However, in accord with the embodiment of FIGURE 5, there is provided an internally disposed conducting bar 60 directly connecting the band contacts 54 and 58. By this arrangement, only three lead in wires are necessary for the particular lamp to ellect parallel connection across the respective filaments.

In actual embodiments of the twin filament lamp as described, the elongated glass enclosure such as the enclosure 10 of FIGURE 1, may be of the order of one-half inch in length with a diameter of approximately threeeighths inch. The resulting miniature lamp is thus not appreciably larger than single filament lamps heretofore available and yet approximately twice the illumination is had with the desired feature of redundancy in the event there should be a failure in one of the filaments.

From the foregoing description, it will thus be evident that the present invention has provided a greatly improved miniature lamp structure particularly suitable for edgelighted panels, annunciator systems, and similar applications wherein compactness is a permanent consideration together with the necessity of meeting specified safety standards.

What is claimed is:

1. A twin filament lamp comprising, in combination: a transparent enclosure in the form of an elongated tube; first and second mounting means disposed at opposite ends of said tube, a first filament generally U-shaped With the legs of said U secured to said first mounting means and the remaining portion of said U extending toward the center of said tube and lying in a first plane; and a second filament generally U-sha-ped with the legs of said .U secured to said second mounting means and the remaining portion of said U extending toward the center of said tube and lying in a second plane substantially at right angles to said first plane, whereby substantially uniform illumination is provided when both filaments are energized.

2. The combination of claim 1, in which said electrical connecting means includes a first pair of flexible lead ,out wires extending from one end of said tube, and a second pair of flexible lead out wires extending from the opposite end of said tube.

3. The combination of claim 1, in which said electrical connecting means includes first and second band contacts respectively encircling the end portions of said tube, and first and second end contacts respectively centrally disposed at the extreme ends of said tube, said first mounting means connecting the two filament legs of said first filament to said first band contact and said first end contact respectively, and said second mounting means connecting the two filament legs of said second filament to said second band contact and second end contact respectively, whereby said tube may be received in a cradle having cooperating springs and end terminals for connection to said band and end contacts.

4. A twin filament lamp comprising, in combination: a transparent enclosure in the form of an elongated tube; first and second mounting means disposed at opposite ends of said tube, a first filament generally U-shaped with the legs of said U secured to said first mounting means and the remaining portion of said U extending toward the center of said tube and lying in a first plane; and a second filament generally U-shaped with the legs of said U secured to said second mounting means and the remaining portion of said U extending toward the center of said tube and lying in a second plane, said tube including a central opaque partition separating said filaments and first and second color filter structures receivable over the opposite ends of said tube such that light from said first filament passes through one of said filters and light from said second filament passes through the other of said filters.

5. A twin filament lamp comprising, in combination: a transparent enclosure in the form of an elongated tube; first and second mounting means disposed at opposite ends of said tube, a first filament generally U-shaped with the legs of said U secured to said first mounting means and the remaining portion of said U extending toward the center of said tube and lying in a first plane; and a second filament generally .U-shaped with the legs of said U secured to said second mounting means and the remaining portion of said U extending toward the center of said tube and lying in a second plane; and

electrical connecting means including first and second band contacts respectively encircling the end portions of said tube, and first and second end contacts respectively centrally disposed at the extreme ends of said tube, said first mounting means connecting the two filament legs 5 ternally connecting said first band contact with said second band contact.

References Cited UNITED STATES PATENTS 1,136,404 4/1915 Buchanan 33956 X 2,267,118 12/1941 Marden 313-109X 3,278,787 10/1966 Bustamente 313318 X 10 JAMES W, LAWRENCE, Primary Examiner.

W. J. SCHWARTZ, Assistant Examiner. 

